1. Field of the Invention
The present invention relates to an apparatus for evaluating an MR (magnetoresistive) head and, more particularly, to an evaluating apparatus for locating a defect within an MR head by using a radiating beam, if such a defect is present.
An MR head is incorporated in a magnetic disk drive that magnetically reads and writes signals to and from a floppy disk or the like. If foreign matter and/or any defect are present in the MR head, read and write operations for reading and writing signals to and from the floppy disk or the like are hampered.
Generally, an electrical tester is used to determine whether an MR head under test is acceptable or defective, as described, for example, in U.S. Pat. No. 5,508,614. However, it is impossible to know where a defect is present on the MR head, if any.
Accordingly, a conceivable method of locating a defect on an MR head is to use an emission method. That is, a voltage of a certain magnitude is applied across a sample, such as an MR head. An electrical current of a given amplitude is passed through the sample. Thus, a defect is made to emit light. The defect is detected, based on the emission.
In this emission method, however, a large electrical current is passed to cause the defect to emit light. Therefore, there is a danger of destruction of the MR head.
It is an object of the present invention to provide a novel apparatus for evaluating a sample, such as an MR head, by locating a defect on the sample without destroying it.
An evaluating apparatus, in accordance with the present invention, evaluates an MR head having a head element, a write electrode, and a read electrode. A head electrode is connected with the head element. The evaluating apparatus comprises a voltage source, a signal detection system, and a radiating beam source. The voltage source is connected with one of the electrodes. The signal detection system includes an amplifier connected with another electrode. The radiating beam source directs a radiating beam to a region including the head element, thus producing an internal photoelectric effect. A signal produced by exciting electrical carriers by the internal photoelectric effect is detected. In this way, a defect on the MR head is detected, if any.
Another evaluating apparatus, in accordance with the present invention, evaluates an MR head having a head element, a write electrode, and a read electrode. A head electrode is connected with the head element. The evaluating apparatus comprises a voltage source, a signal detection system, and a radiating beam source. The voltage source is connected with one of the electrodes. The signal detection system includes an amplifier connected with another electrode. The radiating beam source directs a radiating beam to a region including the head element, thus producing a reflected beam from the region. A reflection image based on the reflected beam from the region and an internal photoelectric effect image based on a signal owing to electrical carriers induced by an internal photoelectric effect are displayed on a display unit in a superimposed manner. This permits a human operator to find a defect on the MR head, if any.
Other objects and features of the invention will appear in the course of the description thereof, which follows.